This application relates generally to fiber-optic communications. This application relates more specifically to techniques and devices for routing different spectral bands of an optical beam.
The Internet and data communications are causing an explosion in the global demand for bandwidth. Fiber optic telecommunications systems are currently deploying a relatively new technology called dense wavelength division multiplexing (DWDM) to expand the capacity of new and existing optical fiber systems to help satisfy this demand. In DWDM, multiple wavelengths of light simultaneously transport information through a single optical fiber. Each wavelength operates as an individual channel carrying a stream of data. The carrying capacity of a fiber is multiplied by the number of DWDM channels used. Today DWDM systems employing up to 80 channels are available from multiple manufacturers, with more promised in the future.
In all telecommunication networks, there is the need to connect individual channels (or circuits) to individual destination points, such as an end customer or to another network. Systems that perform these functions are called cross-connects. Additionally, there is the need to add or drop particular channels at an intermediate point. Systems that perform these functions are called add-drop multiplexers (ADMs). All of these networking functions are currently performed by electronics—typically an electronic SONET/SDH system. However, SONET/SDH systems are designed to process only a single optical channel. Multi-wavelength systems would require multiple SONET/SDH systems operating in parallel to process the many optical channels. This makes it difficult and expensive to scale DWDM networks using SONET/SDH technology.
The alternative is an all-optical network. Optical networks designed to operate at the wavelength level are commonly called “wavelength routing networks” or “optical transport networks” (OTNs). In a wavelength routing network, the individual wavelengths in a DWDM fiber must be manageable. New types of photonic network elements operating at the wavelength level are required to perform the cross-connect, ADM and other network switching functions. Two of the primary functions are optical add-drop multiplexers (OADMs) and wavelength-selective cross-connects (WSXCs).
In various optical-networking applications in optical networks, there is a general need for a two-by-two optical switch that operates on an individual wavelength basis. For example, such two-by-two optical switches may be used as building blocks in larger cross-connect architectures. Specific examples of such larger cross-connect architectures are provided in copending, commonly assigned U.S. patent application Ser. No. 10/093,844, entitled “OPTICAL CROSS CONNECT ARCHITECTURES USING WAVELENGTH ROUTING ELEMENTS,” by Edward J. Bortolini et al., the entire disclosure of which is herein incorporated by reference for all purposes